Here's an amazing project to remove two HEP dams on the Elwha River in North America which will restore a blocked valley to its former wilderness. The project will cost $325 million and began in September 2011. The Seattle Times has full, fascinating coverage on a dedicated project page here.
Here's a quick look at how they're planning to restore the ecology:
Watch the film, 'Kelham Island Hydro', and ask whether what boils down to be a few kettles' worth of hydro-generated electricity is proportionate to the decimation of our little-understood and very fragile river ecosystems.
If you have problems viewing the film from here, please view on Vimeo or watch on Google where you can also download to your pc.